This invention relates to a display managing arrangement for use in displaying a selected region of an image datum on a display screen with the selected region either scrolled on the image datum or otherwise subjected to management.
The display managing arrangement comprises a display memory and a display memory controller in the manner which will later be described in detail. Such a display managing arrangement is already known. For example, a display system with multiple scrolling regions is revealed in U.S. Pat. No. 4,412,294 issued to LaVaughn F. Watts et al and assigned to Texas Instruments Incorporated.
The image datum is typically a two-dimensional image datum. It is usual that the image datum is divided into a plurality of file data which are memorized in a plurality of files, respectively. Two of the file data may or may not have a common datum. On scrolling the selected region as a display part of the image datum, a selected area of the image datum is preliminarily transferred to the display memory and stored therein as an image part from at least one of the files. The display memory is thus loaded with the image part which should have a wider area than the display part. The display memory has serial element addresses at which picture elements of the image part are stored, respectively.
When the display part should be scrolled to include a region beyond the image part stored in the display memory at that time as a first image part, that region must be transferred afresh to the display memory as a new region from the file or files. A considerable portion of the first image part is retained in the display memory as a retained region. Inasmuch as the display memory has a limited memory capacity, a region of the first image part must be deleted from the display memory as a previous region. A second image part is substituted for the first image part in the display memory to comprise the retained and the new regions. In other words, the display memory is renewed or updated.
The display memory controller is used in accessing the display memory on carrying out management thereon, namely, on displaying the display part on the display screen, scrolling the display part, and renewing the display memory. In a conventional display managing arrangement, the display memory controller is typically a graphic display controller for carrying out address control on the display part or on the image part. The conventional display managing arrangement is incapable of, among others, renewing the display memory at a high speed.